Micro light-emitting diode display matrix module

ABSTRACT

The micro light-emitting diode (LED) display matrix module of the disclosure includes a multilayer circuit layer, multiple micro LEDs, and an insulating flat layer. The multilayer circuit layer includes a top circuit layer and a bottom circuit layer. The bottom circuit layer includes multiple pads. The micro LEDs are disposed on the top circuit layer of the multilayer circuit layer and define multiple light-emitting units. Each of the light-emitting units includes three of the micro LEDs that are separated from each other. The light-emitting units are arranged in a matrix of m columns and n rows to define multiple pixel regions, and quantity of the pads is equal to 3m+n. An orthographic projection of each of the micro LEDs on the bottom circuit layer completely overlaps the corresponding pad. The insulating flat layer covers the top circuit layer of the multilayer circuit layer and the micro LEDs.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of U.S. provisionalapplication Ser. No. 63/069,693, filed on Aug. 24, 2020, and Taiwanapplication serial no. 109142526, filed on Dec. 3, 2020. The entirety ofeach of the above-mentioned patent applications is hereby incorporatedby reference herein and made a part of this specification.

BACKGROUND Technical Field

This disclosure relates to a display module, and in particular to amicro light-emitting diode (LED) display matrix module.

Description of Related Art

Currently, splicing of a display screen involves encapsulating the redLEDs, green LEDs and blue LEDs one by one, and then mounting them one byone onto a driving circuit board. Therefore, the size and spacing arelimited, and as each of the LEDs needs two pads, the quantity of thepads cannot be effectively reduced, thereby affecting the bonding yield.In recent years, an encapsulation of micro LEDs matched with anintegrated circuit (IC) has also been proposed, but the thickness isstill not reduced and the bonding process is still time-consuming andirreparable.

SUMMARY

This disclosure provides a micro light-emitting diode (LED) displaymatrix module which effectively reduce the quantity of the pads and isprovided with good surface flatness, therefore to improve the processyield for being bonded to a display circuit board.

The micro LED display matrix module of the disclosure includes amultilayer circuit layer, a plurality of micro LEDs, and an insulatingflat layer. The multilayer circuit layer includes a top circuit layerand a bottom circuit layer. The bottom circuit layer includes aplurality of pads. The micro LEDs are disposed on the top circuit layerof the multilayer circuit layer and define a plurality of light-emittingunits. Each of the light-emitting units includes three of the micro LEDsthat are separated from each other. The light-emitting units arearranged in a matrix of m columns and n rows to define a plurality ofpixel regions, and quantity of the pads is equal to 3m+n. Anorthographic projection of each of the micro LEDs on the bottom circuitlayer completely overlaps the corresponding pad. The insulating flatlayer covers the top circuit layer of the multilayer circuit layer andthe micro LEDs.

In an embodiment of the disclosure, the multilayer circuit layer furtherincludes at least one internal circuit layer and a plurality ofdielectric layers. The internal circuit layer is located between the topcircuit layer and the bottom circuit layer. The dielectric layers arelocated between the top circuit layer, the internal circuit layer, andthe bottom circuit layer.

In an embodiment of the disclosure, a thickness of the top circuit layeris less than a thickness of the internal circuit layer and a thicknessof the bottom circuit layer.

In an embodiment of the disclosure, a circuit pattern density in theinternal circuit layer is greater than a circuit pattern density in thetop circuit layer, and the circuit pattern density in the top circuitlayer is greater than a circuit pattern density in the bottom circuitlayer.

In an embodiment of the disclosure, the multilayer circuit layer furtherincludes a plurality of conductive vias, and the top circuit layer, theinternal circuit layer, and the bottom circuit layer are electricallyconnected through the conductive vias.

In an embodiment of the disclosure, orthographic projections of theconductive vias on the bottom circuit layer do not overlap theorthographic projections of the micro LEDs on the bottom circuit layer.

In an embodiment of the disclosure, the internal circuit layer includesa plurality of circuit patterns, and an orthographic projection of eachof the light-emitting units on the bottom circuit layer completelyoverlaps the corresponding circuit patterns.

In an embodiment of the disclosure, the Young's modulus of theinsulating flat layer is between 10 GPa and 50 GPa.

In an embodiment of the disclosure, a thickness of the insulating flatlayer is at least 5 times greater than a thickness of the multilayercircuit layer.

In an embodiment of the disclosure, the micro LED display matrix modulefurther includes a hard substrate disposed on the insulating flat layer.The insulating flat layer is located between the hard substrate and themultilayer circuit layer.

In an embodiment of the disclosure, a thickness of the hard substrate isgreater than a thickness of the insulating flat layer.

In an embodiment of the disclosure, the micro LED display matrix modulefurther includes an insulation layer, which is disposed on a side of thebottom circuit layer opposite to the internal circuit layer and exposesa part of the pads.

In an embodiment of the disclosure, the insulation layer covers a partof a top surface of the pads.

In an embodiment of the disclosure, a thickness of the insulation layeris greater than a thickness of the bottom circuit layer.

In an embodiment of the disclosure, the micro LED display matrix modulefurther includes a surface treatment layer disposed on the part of thetop surface of the pads exposed by the insulation layer.

In an embodiment of the disclosure, a material of the surface treatmentlayer includes electroless nickel immersion gold (ENIG).

In an embodiment of the disclosure, the micro LED display matrix modulefurther includes a light blocking layer, which is disposed on the topcircuit layer of the multilayer circuit layer, and includes a pluralityof blocking portions. The blocking portions and the light-emitting unitsare in an alternate arrangement.

In an embodiment of the disclosure, a thickness of the light blockinglayer is greater than a thickness of each of the micro LEDs.

In an embodiment of the disclosure, the above-mentioned m>2, and n>2.

In an embodiment of the disclosure, each of the light-emitting unitsfurther includes at least one repair micro LED. An orthographicprojection of the repair micro LED on the bottom circuit layercompletely overlaps the corresponding pad.

Based on the above, in the design of the micro LED display matrix moduleof the disclosure, the light-emitting unit composed of every three microlight-emitting diodes may be arranged in the matrix of m columns and nrows to define the plurality of pixels region, and the quantity of thepads is equal to 3m+n. The orthographic projection of each of thelight-emitting units on the bottom circuit layer completely overlaps thecorresponding pad. In this way, the quantity of the pads can beeffectively reduced, and therefore the micro LED display matrix moduleis with more better surface flatness to improve the process yield forbeing bonded to the display circuit board.

To make the above-mentioned features and advantages more comprehensible,several embodiments accompanied by drawings are described in detail asfollows.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments of thedisclosure and, together with the description, serve to explain theprinciples of the disclosure.

FIG. 1A is a top perspective schematic view of a micro light-emittingdiode (LED) display matrix module according to an embodiment of thedisclosure.

FIG. 1B is an enlarged schematic view of a pixel region of the micro LEDdisplay matrix module in FIG. 1A.

FIG. 1C is a schematic cross-sectional view of the micro LED displaymatrix module in FIG. 1A.

FIG. 2 is a schematic cross-sectional view of a micro LED display matrixmodule according to another embodiment of the disclosure.

FIG. 3 is a schematic top view of a micro LED display matrix moduleaccording to yet another embodiment of the disclosure.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1A is a top perspective schematic view of a micro light-emittingdiode (LED) display matrix module according to an embodiment of thedisclosure. FIG. 1B is an enlarged schematic view of a pixel region ofthe micro LED display matrix module in FIG. 1A. FIG. 1C is a schematiccross-sectional view of the micro LED display matrix module in FIG. 1A.Some layers and components have been omitted in FIG. 1A for clarity.

With reference to FIGS. 1A, 1B, and 1C simultaneously, in theembodiment, a micro LED display matrix module 100 a includes amultilayer circuit layer 110, a plurality of micro LEDs 120R, 120G, and120B, and an insulating flat layer 130. The multilayer circuit layer 110includes a top circuit layer 112 and a bottom circuit layer 114. Thebottom circuit layer 114 includes a plurality of pads 115 that areseparated from each other. The micro LEDs 120R, 120G, and 120B aredisposed on the top circuit layer 112 of the multilayer circuit layer110 and define a plurality of light-emitting units U. Each of thelight-emitting units U includes three micro LEDs 120R, 120G, and 120Bthat are separated from each other. Herein, the three micro LEDs 120R,120G, and 120B in each of the light-emitting units U are a red microLED, a green micro LED, and a blue micro LED, respectively. Inparticular, the light-emitting unit U may be arranged in a matrix of mcolumns and n rows to define a plurality of pixel regions P, andquantity of the pads 115 is equal to 3m+n, where m>2 and n>2. As shownin FIG. 1A, both m and n in the embodiment are 4, therefore there are4*4=16 pixel regions P, and the quantity of the pads 115 is 3*4+4=16. Inaddition, in the embodiment, an orthographic projection of each of themicro LEDs 120R, 120G, and 120B on the bottom circuit layer 114completely overlaps the corresponding pad 115 to be with good flatness.The insulating flat layer 130 covers the top circuit layer 112 of themultilayer circuit layer 110 and the micro LEDs 120R, 120G, and 120B.

Furthermore, with reference to FIGS. 1A and 1C again, the multilayercircuit layer 110 of the embodiment further includes at least oneinternal circuit layer (schematically shown as a single internal circuitlayer 116) and a plurality of dielectric layers (schematically shown astwo dielectric layers 118). The internal circuit layer 116 is locatedbetween the top circuit layer 112 and the bottom circuit layer 114, andthe dielectric layers 118 are located between the top circuit layer 112,the internal circuit layer 116, and the bottom circuit layer 114. Inother words, the top circuit layer 112, the internal circuit layer 116,and the bottom circuit layer 114 are electrically isolated through thedielectric layers 118. A thickness H1 of the top circuit layer 112 isless than a thickness H3 of the internal circuit layer 116 and athickness H2 of the bottom circuit layer 114. Preferably, the thicknessH1 is ½ of the thickness H3 or ½ of the thickness H2.

In particular, a circuit pattern density by the top circuit layer 112and the internal circuit layer 116 in each of the layers of theembodiment is at least greater than 50%, and preferably up to 80%, whichmakes each of the layers to be more even, so that to facilitate asubsequent flip-chip bonding process of the micro LEDs 120R, 120G, and120B and improve the yield. In addition, taking into consideration theprocess limitations such as line width of exposure/etching, or parasiticcapacitance generated between the layers, the circuit patterns densityis preferably not more than 90%. Preferably, the circuit pattern densityin the internal circuit layer 116 is greater than the circuit patterndensity in the top circuit layer 112, and the circuit pattern density inthe top circuit layer 112 is greater than circuit pattern density in thebottom circuit layer 114.

With reference to FIG. 1C, the multilayer circuit layer 110 of theembodiment further includes a plurality of conductive vias 119. The topcircuit layer 112, the internal circuit layer 116, and the bottomcircuit layer 114 are electrically connected through the conductive vias119. That is, the top circuit layer 112 and the internal circuit layer116 are electrically connected through the conductive vias 119, and theinternal circuit layer 116 and the bottom circuit layer 114 are alsoelectrically connected through the conductive vias 119. FIG. 1C onlyshows a cross-section, and only the top circuit layer 112 and theinternal circuit layer 116 are electrically connected through theconductive vias 119 is seen. In another cross-section not shown, theinternal circuit layer 116 and the bottom circuit layer 114 are alsoelectrically connected through the conductive vias 119. In particular,orthographic projections of the conductive vias 119 on the bottomcircuit layer 114 does not overlap the orthographic projections of themicro LEDs 120R, 120G, and 120B on the bottom circuit layer 114. Inother words, in a plan view, none of the position of each of the microLEDs 120R, 120G, and 120B overlaps the position of the conductive vias119. Furthermore, the internal circuit layer 116 of the embodimentincludes a plurality of circuit patterns 117. An orthographic projectionof each of the light-emitting units U on the bottom circuit layer 114completely overlaps the corresponding circuit pattern 117. Herein, theorthographic projection of each of the micro LEDs 120R, 120G, and 120Bon the bottom circuit layer 114 completely overlaps the correspondingcircuit pattern 117.

Furthermore, the insulating flat layer 130 of the embodiment is withhigh visible light transmittance and high Young's modulus. In detail,for example, the visible light transmittance of the insulating flatlayer 130 is greater than 90%, and the Young's modulus is between 10 GPaand 50 GPa. Preferably, the Young's modulus is greater than 30 GPa. Thematerial of the insulating flat layer 130 is, for example, UV-curableacrylate resin or poly methyl pentene (PMP). Preferably, a thickness T2of the insulating flat layer 130 is at least 5 times greater than athickness T1 of the multilayer circuit layer 110. For example, thethickness T2 of the insulating flat layer 130 is, for example, 100 to150 μm, and the thickness T1 of the multilayer circuit layer 110 is, forexample, 20 to 30 μm. Since the insulating flat layer 130 of theembodiment is a hard material, the micro LED display matrix module 100 amay be picked up and bonded by a transfer device, such as an SMT device.

In addition, with reference to FIG. 1C again, the micro LED displaymatrix module 100 a of the embodiment further includes an insulationlayer 140. The insulation layer 140 is disposed on a side of the bottomcircuit layer 114 opposite to the internal circuit layer 116, and a partof the pads 115 is exposed. Furthermore, the insulation layer 140 coversthe surrounding surface and a part of a top surface of each of the pads115, and exposes a middle part of the pads 115. Herein, a thickness H ofthe insulation layer 140 is greater than the thickness H2 of the bottomcircuit layer 114. For example, the thickness H of the insulation layer140 is 10 μm to 15 μm, but it is not limited thereto.

In addition, the micro LED display matrix module 100 a of the embodimentfurther includes a surface treatment layer 150. The surface treatmentlayer 150 is disposed on the part of the top surface of the pads 115exposed by the insulation layer 140. Preferably, the material of thesurface treatment layer 150 is, for example, electroless nickelimmersion gold (ENIG), which can effectively prevent or reduce oxidationof the pads 115 exposed by the insulation layer 140.

In order to effectively reduce the quantity of scraps, the embodimentalso reserves at least one repair position for repair micro LEDs 120P ineach of the pixel regions P (three repair positions are schematicallyshown in FIG. 1B). The repair micro LEDs 120P are separated from eachother and their electrical connections are respectively the same as thatof the micro LEDs 120R, 120G, and 120B, so as to allow replacement ofthe defective or damaged micro LEDs 120R, 120G, and 120B. Herein, anorthographic projection of the repair micro LED 120P on the bottomcircuit layer 114 completely overlaps the corresponding pad 115. Inother words, the repair micro LEDs 120P is not placed when the microLEDs 120R, 120G, 120B are flawless or undamaged. The repair micro LEDs120P are placed to replace the micro LEDs 120R, 120G, and 120B when themicro LEDs 120R, 120G, and 120B are defective or damaged, which canreduce the quantity of micro LED display matrix module 100 a beingscrapped.

In short, in the embodiment, the light-emitting unit U composed of threemicro LEDs 120R, 120G, and 120B may be arranged in the matrix of mcolumns and n rows to define the pixel regions P, and the quantity ofthe pads 115 is equal to 3m+n. Compared with the related art in whicheach of the micro LED needs to be matched with two pads, in theembodiment, only 16 pads 115 are needed for the 48 micro LEDs 120R,120G, and 120B in the 4*4 pixel regions P. The pads 115 may be larger insize and arranged more neatly through the circuit-to-layer design of themultilayer circuit layer 110. Therefore, the above design caneffectively reduce the quantity of the pads 115 and improve thealignment accuracy when the micro LED display matrix module 100 a isdisposed on a display circuit board (not shown) in subsequent process,so as to make the yield better. Furthermore, the micro LED displaymatrix module 100 a of the embodiment is not limited to active drivingor passive driving, hence is more flexible in application. In addition,in the embodiment, the orthographic projection of the light-emittingunit U composed of the three micro LEDs 120R, 120G, and 120B on thebottom circuit layer 114 completely overlaps the corresponding pad 115,which makes the micro LED display matrix module 100 a more even so thatis beneficial to mass transfer process of the micro LEDs 120R, 120G, and120B, and to improve the bonding yield.

It must be noted here that the following embodiments continue to use thereference numerals and part of the content of the foregoing embodiments.The same reference numerals are used to represent the same or similarelements, and the description of the same technical content is omitted.Reference may be made to the foregoing embodiments for the descriptionof the omitted parts, which will not be reiterated in the followingembodiments.

FIG. 2 is a schematic cross-sectional view of a micro LED display matrixmodule according to another embodiment of the disclosure. With referenceto FIG. 1C and FIG. 2 simultaneously, a micro LED display matrix module100 b of the embodiment is similar to the micro LED display matrixmodule 100 a in FIG. 1C, except that in the embodiment, the micro LEDdisplay matrix module 100 b also includes a hard substrate 160 disposedon the insulating flat layer 130. The insulating flat layer 130 islocated between the hard substrate 160 and the multilayer circuit layer110. Preferably, a thickness T3 of the hard substrate 160 is greaterthan the thickness T2 of the insulating flat layer 130. For example, thethickness T3 of the hard substrate 16 is 250 μm and the thickness T2 ofthe insulating flat layer 130 is 80 μm. In the embodiment, theinsulating flat layer 130 is a highly transparent encapsulant, such as ab-stage silicon or epoxy resin, and has Young's modulus between 0.01 GPaand 2 GPa.

In addition, the embodiment also includes a light blocking layer 170,which is disposed on the top circuit layer 112 of the multilayer circuitlayer 110 and includes a plurality of blocking portions 172. Theblocking portions 172 and the light-emitting units U are in an alternatearrangement. Preferably, a thickness T4 of the light blocking layer 170is greater than a thickness T5 of each of the micro LEDs 120. Forexample, the thickness T5 of the micro LED 120 is less than 10 μm, andthe thickness T4 of the light blocking layer 170 is, for example, 15 μmto 30 μm.

In short, since the micro LED display matrix module 100 b of theembodiment includes the hard substrate 160, the micro LED display matrixmodule 100 b has a strong structural strength and may be picked up andbonded by the transfer device, such as the SMT device. In addition, themicro LED display matrix module 100 b of the embodiment also includesthe light blocking layer 170, which blocks reflection of metal circuitand brightness interference between the light-emitting units U, thisprovides the micro LED display matrix module 100 b a good displayeffect.

FIG. 3 is a schematic top view of a micro LED display matrix moduleaccording to yet another embodiment of the disclosure. For theconvenience of description, some components are omitted in FIG. 3. Withreference to FIGS. 1A and 3 simultaneously, a micro LED display matrixmodule 100 c of the embodiment is similar to the micro LED displaymatrix module 100 a in FIG. 1A, except that in the embodiment, thelight-emitting units U may be arranged into a matrix of m columns and nrows, where m=5 and n=5. That is, in the embodiment, there are 5*5=25pixel regions P, and the quantity of pads 115 c 1 and 115 c 2 of abottom circuit layer 114 c is 3*5+5=20. As shown in FIG. 3, a size ofthe pad 115 c 2 of the embodiment is larger than a size of the pad 115 c1, and the pad 115 c 2 spans two of the pixel regions P. An orthographicprojections of the two light-emitting units U located in the two pixelregions P on the bottom circuit layer 114 c completely overlap the pad115 c 2.

In summary, in the design of the micro LED display matrix module of thedisclosure, the light-emitting unit composed of the every three microLED may be arranged in the matrix of m columns and n rows to define theplurality of pixel regions, and the quantity of the pads is equal to3m+n. The orthographic projection of each of the light-emitting units onthe bottom circuit layer completely overlaps the corresponding pad. Inthis way, the quantity of the pads can be effectively reduced, and themicro LED display matrix module can be with good surface flatness,thereby improving the process yield for being bonded to the displaycircuit board.

Although the disclosure has been disclosed with the foregoing exemplaryembodiments, it is not intended to limit the disclosure. Any personskilled in the art can make various changes and modifications within thespirit and scope of the disclosure. Accordingly, the scope of thedisclosure is defined by the claims appended hereto and theirequivalents.

What is claimed is:
 1. A micro light-emitting diode (LED) display matrixmodule, comprising: a multilayer circuit layer, comprising a top circuitlayer and a bottom circuit layer, wherein the bottom circuit layercomprises a plurality of pads; a plurality of micro LEDs, disposed onthe top circuit layer of the multilayer circuit layer, and defining aplurality of light-emitting units, wherein each of the plurality oflight-emitting units comprises three of the plurality of micro LEDs thatare separated from each other, and the plurality of light-emitting unitsare arranged in a matrix of m columns and n rows to define a pluralityof pixel regions, wherein quantity of the plurality of pads is equal to3m+n, and an orthographic projection of each of plurality of the microLEDs on the bottom circuit layer completely overlaps the correspondingpad; and an insulating flat layer, covering the top circuit layer of themultilayer circuit layer and the plurality of micro LEDs.
 2. The microLED display matrix module according to claim 1, wherein the multilayercircuit layer further comprises at least one internal circuit layer anda plurality of dielectric layers, the at least one internal circuitlayer is located between the top circuit layer and the bottom circuitlayer, and the plurality of dielectric layers are located between thetop circuit layer, the at least one internal circuit layer, and thebottom circuit layer.
 3. The micro LED display matrix module accordingto claim 2, wherein a thickness of the top circuit layer is less than athickness of the at least one internal circuit layer and a thickness ofthe bottom circuit layer.
 4. The micro LED display matrix moduleaccording to claim 2, wherein a circuit pattern density in the at leastone internal circuit layer is greater than a circuit pattern density inthe top circuit layer, and the circuit pattern density in the topcircuit layer is greater than a circuit pattern density in the bottomcircuit layer.
 5. The micro LED display matrix module according to claim2, wherein the multilayer circuit layer further comprises a plurality ofconductive vias, and the top circuit layer, the at least one internalcircuit layer, and the bottom circuit layer are electrically connectedthrough the plurality of conductive vias.
 6. The micro LED displaymatrix module according to claim 5, wherein orthographic projections ofthe plurality of conductive vias on the bottom circuit layer do notoverlap the orthographic projections of the plurality of micro LEDs onthe bottom circuit layer.
 7. The micro LED display matrix moduleaccording to claim 2, wherein the at least one internal circuit layercomprises a plurality of circuit patterns, and an orthographicprojection of each of the plurality of light-emitting units on thebottom circuit layer completely overlaps the corresponding circuitpatterns.
 8. The micro LED display matrix module according to claim 1,wherein the Young's modulus of the insulating flat layer is between 10GPa and 50 GPa.
 9. The micro LED display matrix module according toclaim 1, wherein a thickness of the insulating flat layer is at least 5times greater than a thickness of the multilayer circuit layer.
 10. Themicro LED display matrix module according to claim 1, furthercomprising: a hard substrate, disposed on the insulating flat layer,wherein the insulating flat layer is located between the hard substrateand the multilayer circuit layer.
 11. The micro LED display matrixmodule according to claim 10, wherein a thickness of the hard substrateis greater than a thickness of the insulating flat layer.
 12. The microLED display matrix module according to claim 1, further comprising: aninsulation layer, disposed on a side of the bottom circuit layeropposite to the at least one internal circuit layer, and exposing a partof the plurality of pads.
 13. The micro LED display matrix moduleaccording to claim 12, wherein the insulation layer covers a part of atop surface of the plurality of pads.
 14. The micro LED display matrixmodule according to claim 12, wherein a thickness of the insulationlayer is greater than a thickness of the bottom circuit layer.
 15. Themicro LED display matrix module according to claim 13, furthercomprising: a surface treatment layer, disposed on the part of the topsurface of the plurality of pads exposed by the insulation layer. 16.The micro LED display matrix module according to claim 15, wherein amaterial of the surface treatment layer comprises electroless nickelimmersion gold (ENIG).
 17. The micro LED display matrix module accordingto claim 1, further comprising: a light blocking layer, disposed on thetop circuit layer of the multilayer circuit layer, and comprising aplurality of blocking portions, wherein the plurality of blockingportions and the plurality of light-emitting units are in an alternatearrangement.
 18. The micro LED display matrix module according to claim17, wherein a thickness of the light blocking layer is greater than athickness of each of the plurality of micro LEDs.
 19. The micro LEDdisplay matrix module according to claim 1, wherein m>2 and n>2.
 20. Themicro LED display matrix module according to claim 1, wherein each ofthe plurality of light-emitting units further comprises at least onerepair micro LED, and an orthographic projection of the at least onerepair micro LED on the bottom circuit layer completely overlaps thecorresponding pad.